Data.Attoparsec.Text.Lazy

Simple, efficient combinator parsing that can consume lazy Text strings, loosely based on the Parsec library.

This is essentially the same code as in the Text module, only with a parse function that can consume a lazy Text incrementally, and a Result type that does not allow more input to be fed in. Think of this as suitable for use with a lazily read file, e.g. via readFile or hGetContents.

Note: The various parser functions and combinators such as string still expect strict Text parameters, and return strict Text results. Behind the scenes, strict Text values are still used internally to store parser input and manipulate it efficiently.

Documentation

data Result r

The result of a parse.

Constructors

Fail Text [String] String

The parse failed. The Text is the input that had not yet been consumed when the failure occurred. The [String] is a list of contexts in which the error occurred. The String is the message describing the error, if any.

Done Text r

The parse succeeded. The Text is the input that had not yet been consumed (if any) when the parse succeeded.

Instances

Functor Result

Defined in Data.Attoparsec.Text.Lazy

Methods

fmap :: (a -> b) -> Result a -> Result b

(<$) :: a -> Result b -> Result a

Show r => Show (Result r)

Defined in Data.Attoparsec.Text.Lazy

Methods

showsPrec :: Int -> Result r -> ShowS

show :: Result r -> String

showList :: [Result r] -> ShowS

NFData r => NFData (Result r)

Defined in Data.Attoparsec.Text.Lazy

Methods

rnf :: Result r -> ()

data Number

A numeric type that can represent integers accurately, and floating point numbers to the precision of a Double.

Note: this type is deprecated, and will be removed in the next major release. Use the Scientific type instead.

Constructors

I !Integer

D !Double

Instances

Eq Number

Defined in Data.Attoparsec.Number

Methods

(==) :: Number -> Number -> Bool

(/=) :: Number -> Number -> Bool

Fractional Number

Defined in Data.Attoparsec.Number

Methods

(/) :: Number -> Number -> Number

recip :: Number -> Number

fromRational :: Rational -> Number

Data Number

Defined in Data.Attoparsec.Number

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Number -> c Number

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c Number

toConstr :: Number -> Constr

dataTypeOf :: Number -> DataType

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c Number)

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c Number)

gmapT :: (forall b. Data b => b -> b) -> Number -> Number

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Number -> r

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Number -> r

gmapQ :: (forall d. Data d => d -> u) -> Number -> [u]

gmapQi :: Int -> (forall d. Data d => d -> u) -> Number -> u

gmapM :: Monad m => (forall d. Data d => d -> m d) -> Number -> m Number

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Number -> m Number

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Number -> m Number

Num Number

Defined in Data.Attoparsec.Number

Methods

(+) :: Number -> Number -> Number

(-) :: Number -> Number -> Number

(*) :: Number -> Number -> Number

negate :: Number -> Number

abs :: Number -> Number

signum :: Number -> Number

fromInteger :: Integer -> Number

Ord Number

Defined in Data.Attoparsec.Number

Methods

compare :: Number -> Number -> Ordering

(<) :: Number -> Number -> Bool

(<=) :: Number -> Number -> Bool

(>) :: Number -> Number -> Bool

(>=) :: Number -> Number -> Bool

max :: Number -> Number -> Number

min :: Number -> Number -> Number

Real Number

Defined in Data.Attoparsec.Number

Methods

toRational :: Number -> Rational

RealFrac Number

Defined in Data.Attoparsec.Number

Methods

properFraction :: Integral b => Number -> (b, Number)

truncate :: Integral b => Number -> b

round :: Integral b => Number -> b

ceiling :: Integral b => Number -> b

floor :: Integral b => Number -> b

Show Number

Defined in Data.Attoparsec.Number

Methods

showsPrec :: Int -> Number -> ShowS

show :: Number -> String

showList :: [Number] -> ShowS

NFData Number

Defined in Data.Attoparsec.Number

Methods

rnf :: Number -> ()

compareResults :: (Eq i, Eq r) => IResult i r -> IResult i r -> Maybe Bool

Compare two IResult values for equality.

If both IResults are Partial, the result will be Nothing, as they are incomplete and hence their equality cannot be known. (This is why there is no Eq instance for IResult.)

endOfInput :: forall t. Chunk t => Parser t ()

Match only if all input has been consumed.

atEnd :: Chunk t => Parser t Bool

Return an indication of whether the end of input has been reached.

try :: Parser i a -> Parser i a

Attempt a parse, and if it fails, rewind the input so that no input appears to have been consumed.

This combinator is provided for compatibility with Parsec. attoparsec parsers always backtrack on failure.

(<?>) infix 0

Arguments

:: Parser i a

-> String

the name to use if parsing fails

-> Parser i a

Name the parser, in case failure occurs.

choice :: Alternative f => [f a] -> f a

choice ps tries to apply the actions in the list ps in order, until one of them succeeds. Returns the value of the succeeding action.

option :: Alternative f => a -> f a -> f a

option x p tries to apply action p. If p fails without consuming input, it returns the value x, otherwise the value returned by p.

priority  = option 0 (digitToInt <$> digit)

many' :: MonadPlus m => m a -> m [a]

many' p applies the action p zero or more times. Returns a list of the returned values of p. The value returned by p is forced to WHNF.

 word  = many' letter

many1 :: Alternative f => f a -> f [a]

many1 p applies the action p one or more times. Returns a list of the returned values of p.

 word  = many1 letter

many1' :: MonadPlus m => m a -> m [a]

many1' p applies the action p one or more times. Returns a list of the returned values of p. The value returned by p is forced to WHNF.

 word  = many1' letter

sepBy :: Alternative f => f a -> f s -> f [a]

sepBy p sep applies zero or more occurrences of p, separated by sep. Returns a list of the values returned by p.

commaSep p  = p `sepBy` (char ',')

sepBy' :: MonadPlus m => m a -> m s -> m [a]

sepBy' p sep applies zero or more occurrences of p, separated by sep. Returns a list of the values returned by p. The value returned by p is forced to WHNF.

commaSep p  = p `sepBy'` (char ',')

sepBy1 :: Alternative f => f a -> f s -> f [a]

sepBy1 p sep applies one or more occurrences of p, separated by sep. Returns a list of the values returned by p.

commaSep p  = p `sepBy1` (char ',')

sepBy1' :: MonadPlus m => m a -> m s -> m [a]

sepBy1' p sep applies one or more occurrences of p, separated by sep. Returns a list of the values returned by p. The value returned by p is forced to WHNF.

commaSep p  = p `sepBy1'` (char ',')

manyTill :: Alternative f => f a -> f b -> f [a]

manyTill p end applies action p zero or more times until action end succeeds, and returns the list of values returned by p. This can be used to scan comments:

 simpleComment   = string "<!--" *> manyTill anyChar (string "-->")

(Note the overlapping parsers anyChar and string "-->". While this will work, it is not very efficient, as it will cause a lot of backtracking.)

manyTill' :: MonadPlus m => m a -> m b -> m [a]

manyTill' p end applies action p zero or more times until action end succeeds, and returns the list of values returned by p. This can be used to scan comments:

 simpleComment   = string "<!--" *> manyTill' anyChar (string "-->")

(Note the overlapping parsers anyChar and string "-->". While this will work, it is not very efficient, as it will cause a lot of backtracking.)

The value returned by p is forced to WHNF.

skipMany :: Alternative f => f a -> f ()

Skip zero or more instances of an action.

skipMany1 :: Alternative f => f a -> f ()

Skip one or more instances of an action.

count :: Monad m => Int -> m a -> m [a]

Apply the given action repeatedly, returning every result.

eitherP :: Alternative f => f a -> f b -> f (Either a b)

Combine two alternatives.

feed :: Monoid i => IResult i r -> i -> IResult i r

If a parser has returned a Partial result, supply it with more input.

type Parser = Parser Text

satisfy :: (Char -> Bool) -> Parser Char

The parser satisfy p succeeds for any character for which the predicate p returns True. Returns the character that is actually parsed.

digit = satisfy isDigit
    where isDigit c = c >= '0' && c <= '9'

skip :: (Char -> Bool) -> Parser ()

The parser skip p succeeds for any character for which the predicate p returns True.

skipDigit = skip isDigit
    where isDigit c = c >= '0' && c <= '9'

satisfyWith :: (Char -> a) -> (a -> Bool) -> Parser a

The parser satisfyWith f p transforms a character, and succeeds if the predicate p returns True on the transformed value. The parser returns the transformed character that was parsed.

take :: Int -> Parser Text

Consume exactly n characters of input.

string :: Text -> Parser Text

string s parses a sequence of characters that identically match s. Returns the parsed string (i.e. s). This parser consumes no input if it fails (even if a partial match).

Note: The behaviour of this parser is different to that of the similarly-named parser in Parsec, as this one is all-or-nothing. To illustrate the difference, the following parser will fail under Parsec given an input of "for":

string "foo" <|> string "for"

The reason for its failure is that the first branch is a partial match, and will consume the letters 'f' and 'o' before failing. In attoparsec, the above parser will succeed on that input, because the failed first branch will consume nothing.

stringCI :: Text -> Parser Text

Deprecated: this is very inefficient, use asciiCI instead

Satisfy a literal string, ignoring case.

Note: this function is currently quite inefficient. Unicode case folding can change the length of a string ("ß" becomes "ss"), which makes a simple, efficient implementation tricky. We have (for now) chosen simplicity over efficiency.

asciiCI :: Text -> Parser Text

Satisfy a literal string, ignoring case for characters in the ASCII range.

skipWhile :: (Char -> Bool) -> Parser ()

Skip past input for as long as the predicate returns True.

takeTill :: (Char -> Bool) -> Parser Text

Consume input as long as the predicate returns False (i.e. until it returns True), and return the consumed input.

This parser does not fail. It will return an empty string if the predicate returns True on the first character of input.

Note: Because this parser does not fail, do not use it with combinators such as many, because such parsers loop until a failure occurs. Careless use will thus result in an infinite loop.

takeWhile :: (Char -> Bool) -> Parser Text

Consume input as long as the predicate returns True, and return the consumed input.

This parser does not fail. It will return an empty string if the predicate returns False on the first character of input.

Note: Because this parser does not fail, do not use it with combinators such as many, because such parsers loop until a failure occurs. Careless use will thus result in an infinite loop.

takeText :: Parser Text

Consume all remaining input and return it as a single string.

takeLazyText :: Parser Text

Consume all remaining input and return it as a single string.

scan :: s -> (s -> Char -> Maybe s) -> Parser Text

A stateful scanner. The predicate consumes and transforms a state argument, and each transformed state is passed to successive invocations of the predicate on each character of the input until one returns Nothing or the input ends.

This parser does not fail. It will return an empty string if the predicate returns Nothing on the first character of input.

Note: Because this parser does not fail, do not use it with combinators such as many, because such parsers loop until a failure occurs. Careless use will thus result in an infinite loop.

runScanner :: s -> (s -> Char -> Maybe s) -> Parser (Text, s)

Like scan, but generalized to return the final state of the scanner.

takeWhile1 :: (Char -> Bool) -> Parser Text

Consume input as long as the predicate returns True, and return the consumed input.

This parser requires the predicate to succeed on at least one character of input: it will fail if the predicate never returns True or if there is no input left.

inClass :: String -> Char -> Bool

Match any character in a set.

vowel = inClass "aeiou"

Range notation is supported.

halfAlphabet = inClass "a-nA-N"

To add a literal '-' to a set, place it at the beginning or end of the string.

notInClass :: String -> Char -> Bool

Match any character not in a set.

anyChar :: Parser Char

Match any character.

char :: Char -> Parser Char

Match a specific character.

notChar :: Char -> Parser Char

Match any character except the given one.

peekChar :: Parser (Maybe Char)

Match any character, to perform lookahead. Returns Nothing if end of input has been reached. Does not consume any input.

Note: Because this parser does not fail, do not use it with combinators such as many, because such parsers loop until a failure occurs. Careless use will thus result in an infinite loop.

peekChar' :: Parser Char

Match any character, to perform lookahead. Does not consume any input, but will fail if end of input has been reached.

endOfLine :: Parser ()

Match either a single newline character '\n', or a carriage return followed by a newline character "\r\n".

match :: Parser a -> Parser (Text, a)

Return both the result of a parse and the portion of the input that was consumed while it was being parsed.

isEndOfLine :: Char -> Bool

A predicate that matches either a carriage return '\r' or newline '\n' character.

isHorizontalSpace :: Char -> Bool

A predicate that matches either a space ' ' or horizontal tab '\t' character.

hexadecimal :: (Integral a, Bits a) => Parser a

Parse and decode an unsigned hexadecimal number. The hex digits 'a' through 'f' may be upper or lower case.

This parser does not accept a leading "0x" string.

decimal :: Integral a => Parser a

Parse and decode an unsigned decimal number.

signed :: Num a => Parser a -> Parser a

Parse a number with an optional leading '+' or '-' sign character.

rational :: Fractional a => Parser a

Parse a rational number.

The syntax accepted by this parser is the same as for double.

Note: this parser is not safe for use with inputs from untrusted sources. An input with a suitably large exponent such as "1e1000000000" will cause a huge Integer to be allocated, resulting in what is effectively a denial-of-service attack.

In most cases, it is better to use double or scientific instead.

double :: Parser Double

Parse a Double.

This parser accepts an optional leading sign character, followed by at most one decimal digit. The syntax is similar to that accepted by the read function, with the exception that a trailing '.' is consumed.

Examples

These examples use this helper:

r :: Parser a -> Text -> Result a
r p s = feed (parse p s) mempty

Examples with behaviour identical to read, if you feed an empty continuation to the first result:

r double "3"     == Done "" 3.0
r double "3.1"   == Done "" 3.1
r double "3e4"   == Done "" 30000.0
r double "3.1e4" == Done "" 31000.0
r double "3e"    == Done "e" 3.0

Examples with behaviour identical to read:

r double ".3"    == Fail ".3" _ _
r double "e3"    == Fail "e3" _ _

Example of difference from read:

r double "3.foo" == Done "foo" 3.0

This function does not accept string representations of "NaN" or "Infinity".

number :: Parser Number

Deprecated: Use scientific instead.

Parse a number, attempting to preserve both speed and precision.

The syntax accepted by this parser is the same as for double.

This function does not accept string representations of "NaN" or "Infinity".

scientific :: Parser Scientific

Parse a scientific number.

The syntax accepted by this parser is the same as for double.

digit :: Parser Char

Parse a single digit, as recognised by isDigit.

letter :: Parser Char

Parse a letter, as recognised by isAlpha.

space :: Parser Char

Parse a space character, as recognised by isSpace.

skipSpace :: Parser ()

Skip over white space.

(.*>) :: Text -> Parser a -> Parser a

Deprecated: This is no longer necessary, and will be removed. Use *> instead.

Obsolete. A type-specialized version of *> for Text. Use *> instead.

(<*.) :: Parser a -> Text -> Parser a

Deprecated: This is no longer necessary, and will be removed. Use <* instead.

Obsolete. A type-specialized version of <* for Text. Use *> instead.

Running parsers

parse :: Parser a -> Text -> Result a

Run a parser and return its result.

parseOnly :: Parser a -> Text -> Either String a

Run a parser that cannot be resupplied via a Partial result.

This function does not force a parser to consume all of its input. Instead, any residual input will be discarded. To force a parser to consume all of its input, use something like this:

parseOnly (myParser <* endOfInput)
 

parseTest :: Show a => Parser a -> Text -> IO ()

Run a parser and print its result to standard output.

Result conversion

maybeResult :: Result r -> Maybe r

Convert a Result value to a Maybe value.

eitherResult :: Result r -> Either String r

Convert a Result value to an Either value.